Mechano-chemical de-mixing of metal alloys and mixed materials

ABSTRACT

A physical and chemical method is provided for de-mixing (e.g. extracting, separating, purifying and/or enriching) the metal constituents of an alloy or mixed material into different droplet or solid particle products that are highly enriched in the respective phases of the metal. The method involves for instance but is not limited to, shearing, separating and segregating metallic droplets and particles in a carrier fluid to form other droplets or particles that are each separately highly enriched in one of some, if not of all, of the constituent phases of the alloy or mixed material.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/731,498, filed Jun. 20, 2017, which claims priority and benefit ofprovisional application Ser. No. 62/493,109 filed Jun. 22, 2016, theentire disclosures of whis are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to a physical-chemical method to de-mix(e.g. extract, separate, purify and enrich) metal, and similar/related,constituents of an alloy or a mixture of materials into differentparticulate products that are highly enriched in one component of thealloy or mixture.

BACKGROUND OF THE INVENTION

There are several techniques employed for separating and purifying ofmetal components from metal alloys. These techniques involve forinstance ion exchange separation, selective extraction, solventextraction, and low temperature molten salt smelting.

Vacuum distillation or zone melting or a combination of these techniquesalso have been used to obtain high purity bismuth from alloys thereof.

Phase segregation in metal alloys induced by mechanical stress is wellunderstood from the Cahne-Larche models. Similarly, Effect ofinterfacial surface energy on directional spinodal decomposition indeformable spheres under flow is well-understood as detailed byLowengrub and Co-workers (FDMP, vol. 3, no. 1, pp. 1-19, 2007). Thuo andco-workers have extended this knowledge into the so-called SLICE methodto give patchy particles (PCT/US14/69802 filed Dec. 11, 2014,(WP/2015/089309) and Langmuir, 30, pp. 14308-14313, 2014). Despitetremendous advances in theoretical understanding of spinodaldecomposition, and the prediction that Janus-type particles can beobtained as the ultimate thermodynamically relaxed state in binarysystems, there have been no reports on spinodal decompositions resultingin purification or selective isolation of some components of a mixtureor metal alloy.

SUMMARY OF THE INVENTION

In certain illustrative embodiments of the present invention, a physicaland chemical method is used to de-mix (e.g. separate and/or purify) thephases of a dispersion or emulsion of a metallic alloy or mixture ofmaterial in a fluid. The dispersion or emulsion is dissociated intosmaller particles or droplets respectively which are highly enriched inthe respective metals. In some embodiments, one of the components isselectively drawn to the surface when the interfacial surface tension(between the material and the media) is highly unfavorable andmechanical stress is applied to the material. Other embodiments of theinvention can be practiced by applying mechanical stress to particulateswithout their being in a dispersion or emulsion.

In the illustrative embodiment of the present invention, a binary alloyin liquid form comprising a first metal (e.g. Bi) and a second metal(e.g. Sn) is subject to shear and interfacial stress, using an fluidwith a significantly lower surface tension relative to the metal,leading to fragments that are highly enriched (increased) in the firstmetal (e.g. Bi) and other fragments that are enriched in the secondmetal (e.g. Sn) either in their pure form (oxidation state 0) or inreduced form where a reactive media is used. A similar process is alsoshown to separate the phases of a ternary alloy metal (e.g. here aeutectic metal of Bi, In and Sn elements or components) and of amulti-component material (e.g. here a solid alloy mostly composed withNd, Fe, B and Dy elements or components). The enriched particles can beseparated from each other by e.g. filtration techniques, derivatization,or through differences in their densities, into a respective firstmetal-enriched particle product and a second metal-enriched particleproduct. This separation being a diffusion limited process, fourparameters are engineered to accelerate the separation process, viz; i)surface stress through applying mechanical to promote diffusion of a lowshear modulus component of the alloy or mixture, ii) creating dissimilarinterfaces (large interfacial surface energy between the component andthe fluid media to promote migration of the low surface energy componentof the alloy or mixture to the surface), iii) increasing diffusion of atarget component by increasing the working temperature, and iv)introducing a reactive species that targets selective etching or removal(dissolution) of one or a few of the components of the alloy or mixtureto thermodynamically de-stabilize the alloy or mixture and acceleratespinodal decomposition, therefore enhancing the separation byintroducing a chemically favorable sink to compliment the thermodynamicrelaxation.

The method pursuant to the invention provides a low cost, scalable andfast (one step only) process to separate or purify metal constituents ofvarious binary, ternary, and other alloys or mixtures for use forinstance in recovering metal constituents for recycling, purifyingmetals from ores.

These and other advantages of the present invention will become morereadily apparent from the following detailed description taken with thefollowing drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an EDS image of an undercooled Bi-enriched microparticle,which was obtained after retention from a filter paper (11 μm pore sizefilter paper) and which comprised about 99 weight % Bi, balance Sn.

FIG. 2 is an EDS image of undercooled Bi-enriched microparticles, whichwere obtained after retention from a filter paper (11 μm pore sizefilter paper) and which comprised about 99 weight % Bi, balance Sn.

FIG. 3 is an EDS image of one of the undercooled Bi-enrichedmicroparticles of FIG. 3.

FIG. 4 is an SEM image of Sn oxide microparticles from a post-filteredacetic acid solution of particles that was kept for three weeks and thenimaged following further filtration using paper filter retention of 0.3μm.

FIGS. 5A, 5B show the SEM images of the particles resulting from theillustrative method after 15 minutes (15′) (FIG. 5A) mixing and 30 ormore minutes (30′) (FIG. 5B) mixing. By EDS analysis, the light whitecolored particles are composed with more than 90% weight Bi while greycolored particles are composed with more than 70% weight In. Sn ispresent in solution after having been dissolved by the aceticacid/diethylene glycol solution (not shown).

FIG. 6A shows the SEM images of the particles (Example 4a—Nd—Fe—B—Dyparticles) resulting from the illustrative method after 30 minutesmixing. Light white colored particles are composed of more than 75%weight of rare earth metals (Nd and Dy), while grey colored particlesare composed with more than 40% weight Fe and more than 30% Nd, whichshows that these particles have not yet entirely been separated. AA isacetic acid.

FIGS. 6B and 6C show the SEM images of the particles (Nd—Fe—B—Dy) of theother examples.

DETAILED DESCRIPTION OF THE INVENTION

The present invention describes a physical and chemical method toseparate and/or purify the phases of a dispersion or emulsion of ametallic alloy or mixture of different materials. During the process,small solid particles or liquid droplets of highly enriched phases ofthe respective metals or materials are produced. Separation orpurification is mostly controlled by surface energy, shear modulus,and/or chemical reactivity differences between the constituent metals.Practice of the method of the invention will be illustrated in detailbelow with respect to separation of a binary Bi—Sn eutectic alloy, aternary alloy with respect to the separation of Bi—In—Sn eutectic(Field's metal) and higher order of multi-component solid alloys orintermetallics of Nd—Fe—B—Dy into respective metal constituents atrelatively low temperatures above or below the melting point of thealloy at atmospheric pressure. The method of the invention can bepracticed to separate or purify any multi-constituent media in liquid orsolid state and is not limited to metal alloys and can be practiced withvarious mixed materials including, but not limited to, multi-constituentintermetallic materials; multiple adjacent metallic layers; a mixture ofa metal alloy, intermetallic material, and their passivating ornon-passivating surface oxides or analogous surface reaction products;at least one metal constituent and at least one polymeric constituent;at least one inorganic and/or polymeric constituent; and other materialsas will become apparent from the examples set forth below. Embodimentsof the invention can be practiced by applying any type of mechanicalstress to particulates with or without their being in a dispersion oremulsion. Mechanical stress can include, but is not limited to, shearstress, compressive stress, and any other mechanical stress that effectsmigration of one or more constituents.

The method can be practiced with respect to metal alloys in the solidstate, or in the liquid state having a melting point T_(m) in the rangeof 26 to 1350° C. and above. Alloys with relatively low meltingtemperatures; e.g. a melting point T_(m) less than 250 degrees C., canbe subjected to separation into their metal constituents in ambient ornear ambient conditions at atmospheric pressure.

For purposes of illustration and not limitation, a binary eutectic Bi—Snalloy (57 weight % Bi and 43 weight % Sn having a melting point of about139 degrees C. from Alfa Aesar) is separated using the aforementionedSLICE equipment (however without undercooling of the material ornecessarily making them into particles) pursuant to an embodiment of theinvention into particles (first particle product) that are highlyenriched in Bi (first metal) and different particles (second particleproduct) that are enriched in Sn (second metal). Separation isfacilitated by large surface tension differences between Bi and Sn (e.g.380 mN/m vs. 560 mN/m for Bi and Sn, respectively). SLICE equipment isdescribed in PCT/US14/69802 filed Dec. 11, 2014, (WO/2015/089309) andLangmuir, 30, pp. 14308-14313, 2014, the disclosures of which areincorporated herein by reference.

For example, the liquid (molten) eutectic Bi—Sn alloy is subjected toshearing using the aforementioned SLICE equipment, which embodies anextension of droplet emulsion technique (DET), in the presence of thedilute (about 2%) acetic, acid in diethylene glycol (carrier fluid). Theshearing process involves shearing of liquid (molten) droplets of theeutectic Bi—Sn alloy in the presence of the carrier fluid together withchemical reaction.

In the separation of metal constituents of an alloy pursuant toembodiments of the invention, the following examples are offered:

Constituent Metal Separation—Example 1

Shear stressing under flow and large interfacial surface tension wasused to achieve separation of the Bi and Sn metal constituents. Forexample, an amount [0.6 g (approx.)] of the eutectic Bi—Su alloy wasadded to dilute (about 1 vol. %) acetic acid in diethylene glycolsolution (e.g. 0.1 mL acetic acid in 9.9 mL diethylene glycol). Aceticacid (Biotech, sequencing grade), diethylene glycol (BioUltra) andethanol (200 proof) were purchased from Fisher, Sigma, and OceanLaboratories Inc., respectively.

In Example 1 (JS-1-6A), the acetic acid/diethylene glycol solution(fluid) prepared in a glass vial (scintillation vials, 20 mL) was keptin oil bath at determined thermal stress temperature (160° C.) for atleast 2 min before subjected to shear to make sphericalparticles—spherical particles were desired for ease of analysis but theyare not necessary. Shear was applied using a Dremel 3000 variable speedrotary tool at the rate of 1200 rpm with extender accessory andcross-shaped (or any other desired geometry) poly(tetrafluoroethylene)(PTFE) shearing implement. The shearing implement was placed as close aspossible to vial wall to enhance the effect of shear. Shearing stirringwas conducted for 20 minutes (to make spherical particles) followed bygradual cooling to room temperature with stirring for 60 minutes duringwhich time the phase solidification with concomitant phase separationoccurs. Excess acetic acid and diethylene glycol was washed out withethanol through filtering. Whatman #1 (particle retention of 11 μm), VWRFilter paper 494 (particle retention of 1 μm) and Whatman grade EPM 2000(particle retention of 0.3 μm) filter papers were used for separationand cleaning of particles. Particles were stored in ethanol.

Particle Characterization

The resulting particles were characterized with scanning electronmicroscopy (FEI Quanta 250 FE-SEM). The SEM were operated under highvacuum at the voltage of 8-10 kV. Both the secondary electron and theenergy selective backscattering (EsB) mode were used to image thesamples. Chemical characterization were conducted by energy dispersiveX-Ray spectroscopy (EDS). Additional characterization was performed on aZeiss Supra 55VP Field Emission SEM. Samples were imaged using anelectron beam accelerating voltage of 3 kV and a working distance of 3.3mm. Images were collected using an In-lens detector or anEverhart-Thornley secondary electron detector. Elemental analysis wasperformed at a working distance of 8.5 mm and using electron beamaccelerating voltages of 15 kV. Elemental composition was determinedusing an Energy Dispersive x-ray Spectrometer with a silicon driftdetector.

Example 1 produced a mixture of relatively large, rough-surfaceparticles comprised of almost pure Bi (EDS showed Bi=99.0 weight % ormore) and a precipitate of organometallic Sn. The organometallicprecipitate comprised chelated Sn in high concentration of 75-99 weight% with the impurities being adventitious in nature.

FIG. 2 is an EDS image of an undercooled Bi-enriched microparticle fromExample 1, which comprised about 99 weight % Bi. The microparticle wastaken from a first filtering step of the acetic acid shearing solutionusing filter paper (11 μm filter paper retention).

FIG. 3 is an EDS image of other undercooled Bi-enriched microparticlesfrom Example 1, which were taken from a first filtering step of theacetic acid solution using filter paper (11 μm filter paper retention).FIG. 4 is an EDS image of one of the undercooled Bi-enrichedmicroparticles of FIG. 3.

FIG. 4 is an SEM image of precipitated Sn from a post-filtered aceticacid solution of particles that was kept for three weeks of Example 1and then imaged following further filtration using paper filterretention of 0.3 μm. The Sn precipitate are primarily Sn adducts.

Example 1 demonstrates that the binary Bi—Sn eutectic alloy will beseparated by practice of illustrative embodiments of the invention intoparticles that are highly enriched in Bi metal and to different Sn oxideparticles that are highly enriched in Sn. The different particles were

Separation of Constituent Metal Separation—Example 2

The example involved applying shear stress under flow and largeinterfacial surface tension to achieve separation of the Cu from ashredded yellow brass alloy 260 sheet (shredded alloy chips of 0.25inch×0.25 inch×0.025 inch in a manner similar to the examples 1 and 3 ata thermal stress temperature of 130° C. The Cu was separated as copperhydroxide, which formed as a result of the shearing process in thecarrier fluid and can be treated to recover the copper content;concomitantly, the zinc is recovered as aggregates that vary in sizefrom a few micrometers to millimeter scale.

Separation of ternary materials with the Example 3 of Bi—In—Sn eutectic(Field's metal, 32.5% weight Bi, 51% weight In, 16.5% weight Sn):

Constituent Metal Separation

For the separation of the ternary metal, a similar process was used: anamount (2 g. approx.) of the eutectic Bi—In—Sn alloy was added to adiluted solution (about 5 vol. %) of acetic acid in diethylene glycol(e.g. 2.5 mL acetic acid in 47.5 mL Methylene glycol). Acetic acid(Biotech, sequencing grade), diethylene glycol (BioUltra) and ethanol(200 proof) were purchased from Fisher Sigma, and Decon LaboratoriesInc., respectively.

In Example 3 (CF-1-47), the acetic acid and diethylene glycol solution(fluid) was first poured in a soup maker (Cuisinart SBC-1000Blend-and-Cook Soup Maker) and heated up to an approximately constanttemperature of 85° C. The metal is then poured in the solution and keptapproximately 2 minutes in solution to allow melting of the alloy beforebeing sheared (the temperature is maintained at approximately 85° C. forthe entire experiment). Shear was applied by the soup maker bladesrotating at 7500 rpm. Shearing stirring was conducted for up to 60minutes. The excess of solution of acetic acid and diethylene glycol waswashed out with ethanol through filtering Whatman grade EPM 2000(particle retention of 0.3 μm) filter papers were used for separationand cleaning of particles. Particles were stored in ethanol.

FIG. 5A shows the SEM images as well as the EDS analysis of theparticles resulting from this mixing process after 15 minutes (FIG. 5A)mixing and 45 minutes (FIG. 5B) mixing. Light white colored particlesare composed with more than 90% weight Bi while grey colored particlesare composed with more than 70% weight In. Sn is present in solutionafter having been dissolved by the acetic acid/diethylene glycolsolution (not shown). Fifteen (15) minutes shearing time seem to besufficient here (with the chemical, mechanical and thermal conditionsmentioned above) to separate entirely each phases of the materials intopurified particles of each constituents, as exemplified by FIG. 5Bobtained in the SEM from particles that have been sheared approximately45 minutes.

Separation of multi-component materials with the Example 4 of Nd—F3—B—Dyintermetallic magnetic particles (50-55% wt. Fe, 30-35% wt. Nd, 5-10%Dy, ≈7% wt. B, traces of Co, Cu, Al, Ni): This intermetallic materialsystem of constituents was selected because of the differences ininterfacial energy (surface tension), elastic properties (Young's shearmodulus and shear modulus) and chemical reactivity of the constituentphases as well as the critical importance rare earth metals.

Constituent Metal Separation

For the separation of the multi-component metallic alloy, a similarprocess was used: an amount (2 g. approx.) of the NdFeB crushedmillimeter-size solid particles was added to a diluted solution ofacetic acid in diethylene glycol. Acetic acid (Biotech, sequencinggrade), diethylene glycol (BioUltra) and ethanol (200 proof) werepurchased from Fisher, Sigma, and Decon Laboratories Inc., respectively.

In Example 4a (CF-2-7), the acetic acid (200 μL) and diethylene glycol(≈50 mL) solution (fluid) was first poured in a soup maker (CuisinartSBC-1000 Blend-and-Cook Soup Maker) and maintained at a temperature ofapproximately 55° C. Shear was applied by the soup maker blades rotatingat 17,000 rpm. Shearing stirring was conducted for up to 180 minutes.The excess of solution of acetic acid and diethylene glycol was washedout with ethanol through filtering. Whatman grade EPM 2000 (particleretention of 0.3 μm) filter papers were used for separation and cleaningof particles. Particles were stored in ethanol.

In Example 4b (CF-2-6), the acetic acid (200 μL) and diethylene glycol(≈50 mL) solution (fluid) was first poured in a soup maker (CuisinartSBC-1000 Blend-and-Cook Soup Maker) and maintained at a temperature ofapproximately 100° C. Shear was applied by the soup maker bladesrotating at 7800 rpm. Shearing stirring was conducted for up to 180minutes. The excess of solution of acetic acid and diethylene glycol waswashed out with ethanol through filtering, What an grade EPM 2000(particle retention of 0.3 μm) filter papers were used for separationand cleaning of particles. Particles were stored in ethanol.

FIG. 6A shows the SEM images as well as the EDS analysis of theparticles (Example 4a) resulting from this mixing process after 30minutes mixing. Light white colored particles are composed with morethan 75% weight of rare Earth metals (Nd and Dy) while grey coloredparticles are composed with more than 40% weight Fe and more than 30%Nd, which shows that these particles have not yet entirely beenseparated. Other materials are also listed on the EDS results with amuch minor importance (<10% weight). Fe is mostly dissolved and presentin the solution obtained after filtration of the particles and beforerinsing with Ethanol (not shown here). In all the other examples (FIGS.6B and 6C), the SEM and EDS analysis confirm the presence of more than75% weight of rare Earth metals in light white colored particles.

In the above Examples, although a Dremel driven tool or commercialblender was used to apply shear at the indicated mixer rpm, higher rpmvalues can be used to produce higher shear stress. By adapting the timeof the mixing process and the rotational speed, one can obtain similarresults if other parameters such as chemical composition or temperatureof the etchant are kept constant. The rotational speed of the mixerblades controls the shear forces acting on the particle. In addition tothe Dremel driven tool and commercial blender described above forillustration, a Silverson Model L5M-A overhead lab mixer can be for usedin practice of the invention for further purposes of illustration toprovide an rpm value of 10,000 rpm.

Although Example 1 (JS-1-6A) above employed the low melting Bi—Sneutectic alloy in the liquid state for purposes of illustration, alloyswith higher melting point, T_(m), than the binary Bi—Sn eutectic can beseparated using embodiments of the invention wherein the mediumcomprises a material such as an ionic liquid [e.g. (BMIM)(PFNFSI) whichdecomposes at T_(d) of 290° C. and quaternary ammonium ionic liquids];or polar hydrocarbon liquid (e.g. polyphenyl ether pump fluid, boilingpoint T_(b) approximately 475° C. at 760 mmHg) having a higher meltingpoint that allows the process to be practiced at the suitabletemperature. (BMIM)(PFNFSI) is 1-butyl-3-methylimidazoliumN-pentafluorphenylnonafluorbutylsulfonamide. Other ionic liquids havingappropriate T_(m)'s that can be used below their decompositiontemperature (T_(d)) and above their T_(m) are described in Zhang,Physical Properties of Ionic Liquids: Database and Evaluation, J. Phys,Chem. of Data, Vol. 35, No. 4, 2006, the disclosure of which isincorporated herein by reference, and include, but are limited to,[NH₄][NO₃]; [TMA][BF₄]; [TEA][BF₄]; [TPA][BF₄]; [TBA][BF₄] where TMA istetramethyl ammonium; TEA is tetraethyl ammonium; TPA is tetramylammonium; and TBA is tetrabutyl ammonium. These media can be used toshear higher melting point alloys in their liquid or molten state,although as demonstrated above alloys can be sheared in their solidparticulate state. Moreover, although the above examples employedcertain liquid fluids for the shearing step, other fluids that can beused in a shearing step include air or other gases.

Separation of multi-mixed materials with the Example 5 of bondedNd—Fe—B—Dy magnet (NdFeBDy magnetic particles in a Nylon matrix): Thissystem of constituents were selected because of the differences ininterfacial energy (surface tension), elastic properties (Young's shearmodulus and shear modulus) and chemical reactivity of the constituentphases as well as the ethical importance of rare earth metals.Constituent Metal Separation

For the separation of this multi-mixed material, the bonded magnet wasplaced in a solvent that swells (chemical stresses) the Nylon polymermatrix in a shearing apparatus so that the solvent is used as thecarrier fluid for the shearing process, which is conducted in concurrentmanner at a temperature of 90° C. using 1200 rpm magnetic stirrer for2-6 hrs (depending on quantity). The solvent was water, a solution ofacetic acid and di-ethylene glycol, or dichloromethane. The carrierfluid was filtered with a Whatman no. 1 filter paper, which revealedthat the concurrent application of the shearing force to the swollenmaterial separated the denser NdFeB phase of the mixed material so thatthe NdFeB particles were sheared pursuant to the invention as describedabove to separate the rare earth metals Nd and Dy together in the sameparticles from the Fe and B which remain in the carrier fluid. Thepolymer and carrier fluid are collected as the filtrate, while the solidmagnetic particulates are obtained on the filter paper. Repeated washingof the solids can be used to remove any residual polymeric material.Alternately, the method embodiment of this example can be conductedusing separate steps of first swelling the Nylon polymer matrix and thensubjecting the swollen mixed material to the shearing process.

Separation of multi-mixed materials with the Example 6 of amicroelectronic motherboard having soldered gold electrical connections:

Constituent Separation

For the separation of this multi-mixed material, small cut pieces of themicroelectronic inorganic motherboard (from an electronics recyclingfacility) are cleaned and placed in a solvent, such as dichloromethane,that swells the mostly polyurethane glue layer beneath a conventionaladlayer (either iron or zinc layer on which the gold is deposited andsoldered) in a shearing apparatus of the type described above using amagnetic stirrer rotated at 500 rpm at room temperature for three days.At the end of the shearing process, the solution was filtered with aWhatman no. 1 filter paper (11 μm pore size), and the recovered materialwas placed in a scintillation vial in ethanol. The concurrentapplication of the shearing force to the cut pieces was found toseparate the denser gold material from the adjacent Fe or Zn adlayer andany remaining solder. Alternately, the method embodiment of this examplecan be conducted using separate steps of first removing the solder andthen subjecting the motherboard pieces to the shearing process torecover the gold.

Air-Driven Separation of Constituent Metal Separation—Example 7

Shear stressing under flow and large interfacial surface tension wasused to achieve separation of FM (Sn—Bi) alloy using hot air as theshearing fluid directed from a laboratory hot air dryer across polishedFM particles. A tin oxide surface reaction product was observed to belocated on and to peel off of the surfaces of the FM particles after theair-driven shearing process to de-mix the Cu from the alloy. Thisexample is offered to illustrate that shearing fluids other than liquidscan be used in practice of embodiments of the invention. Also, theexample illustrates shear stress the mixed particulates without theirbeing in a dispersion or emulsion.

The present invention can be practiced to recover metal constituents ofan alloy for recycling and for purifying metals that contain unwantedmetal constituent(s). The unwanted metal constituent(s) can be removed(separated out) from the wanted metal by practice of the invention.

Although the present invention has been described with respect tocertain illustrative embodiments, those skilled in the art willappreciate is not limited to these embodiments and that changes andmodifications can be made therein within the scope of the invention asset forth in the appended claims.

We claim:
 1. A method for de-mixing constituents of a mixed material,comprising applying at least one of mechanical stress, thermal stress,and chemical stress to particulates of the mixed material in a fluid,wherein the mixed material comprises a first metal and a secondmaterial, wherein the mechanical stress, thermal stress, or chemicalstress is applied under conditions to achieve de-mixing of at least oneof the constituents of the mixed material to form a first particleproduct that is enriched in the first metal relative to the mixedmaterial and to form a second product dissolved in the fluid, whereinthe second product is enriched in the second material relative to themixed material.
 2. The method of claim 1, wherein the mixed materialcomprises a metal alloy comprising a liquid alloy and/or a solid alloy.3. The method of claim 1, wherein the mixed material comprises a firstmetal layer and an adjacent second metal layer.
 4. The method of claim1, wherein the mixed material comprises NdFeBDy.
 5. The method of claim1, wherein a polymer comprises the mixed material.
 6. The method ofclaim 5, wherein the polymer matrix comprises nylon.
 7. The method ofclaim 5, wherein mixed material comprises NdFeBDy.
 8. The method ofclaim 5, wherein the fluid swells the polymer matrix to separate themixed material therefrom.
 9. The method of claim 1, wherein a magnetcomprising a nylon matrix comprises the mixed material, wherein themixed material comprises NdFeBDy particles.
 10. The method of claim 1,wherein the mixed material comprises yellow brass.
 11. The method ofclaim 1, wherein the fluid comprises a liquid, a gas, a reactive fluidthat selectively etches or dissolves at least one of the constituents ofthe mixed material, or a combination thereof.
 12. The method of claim 1,wherein the fluid comprises a liquid.
 13. The method of claim 1, whereinthe fluid comprises acetic acid, diethylene glycol, water,dichlorornethane, ethanol, an ionic liquid, or a combination thereof.14. The method of claim 1, wherein the first metal comprises a rareearth metal.
 15. The method of claim 1, wherein the first metalcomprises Nd, Dy, Zn, or a combination thereof.
 16. The method of claim1, wherein the second material comprises a metal, an organometallicmaterial, a polymer, an inorganic material, or a combination thereof.17. The method of claim 1, wherein the second material comprises Cu, Fe,B, or a combination thereof.
 18. The method of claim 1, wherein thesecond product comprises Cu(OH)₂, Fe, B, or a combination thereof. 19.The method of claim 1, wherein: the mixed material comprises yellowbrass; the first metal comprises Zn; the second material comprises Cu;and the second product comprises Cu(OH)₂.
 20. The method of claim 1,wherein: a magnet comprising a polymer matrix comprises the mixedmaterial; the mixed material comprises NdFeBDy particles; the fluidswells the polymer matrix to separate the mixed material therefrom; thefirst metal comprises Nd and Dy; and the second product comprises Fe andB.